How do I delete a tag?

On the My Tags page, delete any tag you no longer need.

What happens to tagged items

Deleting a tag only removes the label — it does not delete any of your pieces, sets, or wantlist items. The tag simply comes off whatever it was applied to, and everything else stays exactly as it was.

So it's perfectly safe to clean up old tags. If you later want it back, just create it again (you have a generous allowance — see How many tags can I have, and what colors?).